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<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> Vector result = new Vector(lhs);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> result.x += rhs.x;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> result.y += rhs.y;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> result.z += rhs.z;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> return result;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="2" style="MARGIN: 0cm 0cm 8.15pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">}</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">运算符声明的方式与方法声明的方式相同，但</span><span lang="EN-US">operator</span><span style="FONT-FAMILY: 宋体">关键字告诉编译器，它实际上是一个运算符重载，</span><span style="FONT-FAMILY: 宋体">后面是相关运算符的符号，在本例中就是</span><span lang="EN-US">+</span><span style="FONT-FAMILY: 宋体">。返回类型是在使用这个运算符时获得的类型。在本例中，把两个矢量加起来会得到另一个矢量，所以返回类型就是</span><span lang="EN-US" style="COLOR: black">Vector</span><span style="COLOR: black; FONT-FAMILY: 宋体">。对于这个</span><span lang="EN-US" style="COLOR: black">+</span><span style="COLOR: black; FONT-FAMILY: 宋体">运算符重载，返回类型与包含类一样，但这种情况并不是必需的。两个参数就是要操作的对象。对于二元运算符</span><span lang="EN-US" style="COLOR: black">(</span><span style="COLOR: black; FONT-FAMILY: 宋体">带两个参数</span><span lang="EN-US" style="COLOR: black">)</span><span style="COLOR: black; FONT-FAMILY: 宋体">，如</span><span lang="EN-US" style="COLOR: black">+</span><span style="COLOR: black; FONT-FAMILY: 宋体">和－运算符，第一个参数</span><span style="FONT-FAMILY: 宋体">是放在运算符左边的对象或值，第二个参数是放在运算符右边的对象或值。</span></p>
<p class="MsoNormal"><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">要求所有的运算符都声明为</span><span lang="EN-US">public</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">static</span><span style="FONT-FAMILY: 宋体">，这表示它们与它们的类或结构相关联，而不是与对象相关联，所以运算符重载的代码体不能访问非静态类成员，也不能访问</span><span lang="EN-US">this</span><span style="FONT-FAMILY: 宋体">指针；这是可以的，因为参数提供了运算符执行任务所需要知道的所有数据。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">前面介绍了声明运算符</span><span lang="EN-US">+</span><span style="FONT-FAMILY: 宋体">的语法，下面看看运算符内部的情况：</span></p>
<p class="a6" style="MARGIN: 8.15pt 0cm 0pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> Vector result = new Vector(lhs);</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> result.x += rhs.x;</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> result.y += rhs.y;</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> result.z += rhs.z;</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> return result;</span></p>
<p class="a6" style="MARGIN: 0cm 0cm 8.15pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">这部分代码与声明方法的代码是完全相同的，显然，它返回一个矢量，其中包含前面定义的</span><span lang="EN-US">lhs</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">rhs</span><span style="FONT-FAMILY: 宋体">的和，即把</span><span lang="EN-US">x</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">y</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">z</span><span style="FONT-FAMILY: 宋体">分别相加。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">下面需要编写一些简单的代码，测试</span><span lang="EN-US">Vector</span><span style="FONT-FAMILY: 宋体">结构：</span></p>
<p class="2" style="MARGIN: 8.15pt 0cm 0pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> static void Main()</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> Vector vect1, vect2, vect3;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> vect1 = new Vector(3.0, 3.0, 1.0);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> vect2 = new Vector(2.0,­­­</span><span style="FONT-FAMILY: 宋体">–</span><span lang="EN-US">4.0,</span><span style="FONT-FAMILY: 宋体">–</span><span lang="EN-US">4.0);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> vect3 = vect1 + vect2;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> Console.WriteLine("vect1 = " + vect1.ToString());</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> Console.WriteLine("vect2 = " + vect2.<span style="LETTER-SPACING: -0.2pt">ToString</span>());</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> Console.WriteLine("vect3 = " + vect3.ToString());</span></p>
<p class="2" style="MARGIN: 0cm 0cm 8.15pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">把这些代码保存为</span><span lang="EN-US">Vectors.cs</span><span style="FONT-FAMILY: 宋体">，编译并运行它，结果如下：</span></p>
<p class="a3" style="MARGIN-TOP: 8.15pt; TEXT-INDENT: 21.45pt"><span lang="EN-US">Vectors</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">vect1 = ( 3 , 3 , 1 )</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">vect2 = ( 2 ,</span><span style="FONT-FAMILY: 宋体">–</span><span lang="EN-US">4 ,</span><span style="FONT-FAMILY: 宋体">–</span><span lang="EN-US">4 )</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">vect3 = ( 5 ,</span><span style="FONT-FAMILY: 宋体">–</span><span lang="EN-US">1 ,</span><span style="FONT-FAMILY: 宋体">–</span><span lang="EN-US">3 )</span></p>
<h4 style="TEXT-INDENT: 21.45pt"><span lang="EN-US">1. </span><span style="FONT-FAMILY: 黑体">添加更多的重载</span></h4>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">矢量除了可以相加之外，还可以相乘、相减，比较它们的值。本节通过添加几个运算符重载，扩展了这个例子。这并不是一个功能全面的真实的</span><span lang="EN-US">Vector</span><span style="FONT-FAMILY: 宋体">类型，但足以说明运算符重载的其他方面了。首先要重载乘法运算符，以支持一个标量和多个矢量的相乘以及一个矢量和多个矢量的相乘。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">一个矢量乘以一个标量只是矢量的元素分别与标量相乘，例如，</span><span lang="EN-US">2 * (1.0, 2.5, 2.0)</span><span style="FONT-FAMILY: 宋体">就等于</span><span lang="EN-US">(2.0, 5.0, 4.0)</span><span style="FONT-FAMILY: 宋体">。相关的运算符重载如下所示。</span></p>
<p class="2" style="MARGIN: 6.5pt 0cm 0pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> public static Vector operator * (double lhs, Vector rhs)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> return new Vector(lhs * rhs.x, lhs * rhs.y, lhs * rhs.z);</span></p>
<p class="2" style="MARGIN: 0cm 0cm 6.5pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">但这还不够，如果</span><span lang="EN-US">a</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">b</span><span style="FONT-FAMILY: 宋体">被声明为</span><span lang="EN-US">Vector </span><span style="FONT-FAMILY: 宋体">类型，就可以编写下面的代码：</span></p>
<p class="2" style="MARGIN: 4.9pt 0cm 4.9pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">b = 2 * a;</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">编译器会隐式地把整数</span><span lang="EN-US" style="LETTER-SPACING: 0.1pt">2</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">转换为</span><span lang="EN-US" style="LETTER-SPACING: 0.1pt">double</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">类型，以符合运算符重载的要求。但不能编译下面的代码：</span></p>
<p class="2" style="MARGIN: 4.9pt 0cm 4.9pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">b = a * 2;</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 15pt"><span style="FONT-FAMILY: 宋体">编译器处理运算符重载的方式和处理方法重载的方式是一样的。它会查看给定运算符的所有可用重载，找到与之最匹配的那个运算符重载。上面的语句要求第一个参数是一个</span><span lang="EN-US">Vector</span><span style="FONT-FAMILY: 宋体">，第二个参数是一个整数，或者可以隐式转换为整数的其他数据类型。我们没有提供这样一个重载。有一个运算符重载，其参数是一个</span><span lang="EN-US">double</span><span style="FONT-FAMILY: 宋体">和一个</span><span lang="EN-US">Vector</span><span style="FONT-FAMILY: 宋体">，但编译器不能改变参数的顺序，所以这是不行的。还需要显式定义一个运算符重载，其参数是一个</span><span lang="EN-US">Vector</span><span style="FONT-FAMILY: 宋体">和一个</span><span lang="EN-US">double</span><span style="FONT-FAMILY: 宋体">，有两种方式可以定义这样一个运算符重载，第一种方式和处理所有的运算符的方式一样，显式中断矢量相乘操作：</span></p>
<p class="2" style="MARGIN: 4.9pt 0cm 0pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> public static Vector operator * (Vector lhs, double rhs)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> return new Vector(rhs * lhs.x, rhs * lhs.y, rhs *lhs.z);</span></p>
<p class="2" style="MARGIN: 0cm 0cm 6.5pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">假定已经编写了执行相乘操作的代码，最好重复使用该代码：</span></p>
<p class="2" style="MARGIN: 4.9pt 0cm 0pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> public static Vector operator * (Vector lhs, double rhs)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> return rhs * lhs;</span></p>
<p class="2" style="MARGIN: 0cm 0cm 6.5pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US"> }</span></p>
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